Support for arbitrary non-integer objects

[n1ngu]

Some objects might represent integers, and implement basic arithmetic operations with integers (+1 and //2) through https://docs.python.org/3/reference/datamodel.html#emulating-numeric-types

While they are not python numbers, they could still be paired with this library.

E.g. objects representing database columns, futurized integer results, arbitrary formula engines, etc, etc.

Simply removing the integer cast in the pairing function should do the trick.

The usage should be documented to call the pairing function with the safe=False flag, since depairing will generally be not possible.

[n1ngu]

#3 would solve this (except for the documentation concern)